[resolved] Can't edit style.css of main domain any more after installing multi-site (3 posts)

I have installed multi-site for WordPress 3.4.1. I can edit the style.css (and other files) of a subdomein but I can't edit the style.css of my main domain as the theme-editor isn't visible anymore under 'Appearence'.

I have removed the multi-site installation and now I'm able to use the theme-editor again. I still want to use a multi-site installation as it will work very efficient for me. Can somebody help?